Editing Exon (section)

==History==
The term ''exon'' is a shortening of the phrase ''expressed region'' and was coined by American [[biochemist]] [[Walter Gilbert]] in 1978: "The notion of the [[cistron]]... must be replaced by that of a transcription unit containing regions which will be lost from the mature messenger{{spaced ndash}}which I suggest we call introns (for intragenic regions){{spaced ndash}}alternating with regions which will be expressed{{spaced ndash}}exons."<ref>{{cite journal |author=Gilbert W |title=Why genes in pieces? |journal=Nature |volume=271 |issue=5645 |pages=501 |date=February 1978 |pmid=622185 |doi=10.1038/271501a0|bibcode=1978Natur.271..501G |doi-access=free }}</ref>

This definition was originally made for protein-coding transcripts that are spliced before being translated.  The term later came to include sequences removed from [[rRNA]]<ref>{{cite journal |vauthors=Kister KP, Eckert WA |title=Characterization of an authentic intermediate in the self-splicing process of ribosomal precursor RNA in macronuclei of Tetrahymena thermophila |journal=Nucleic Acids Research |volume=15 |issue=5 |pages=1905–20 |date=March 1987 |pmid=3645543 |pmc=340607 |doi=10.1093/nar/15.5.1905}}</ref> and [[tRNA]],<ref>{{cite journal |vauthors=Valenzuela P, Venegas A, Weinberg F, Bishop R, Rutter WJ|title=Structure of yeast phenylalanine-tRNA genes: an intervening DNA segment within the region coding for the tRNA |journal=Proceedings of the National Academy of Sciences of the United States of America |volume=75 |issue=1 |pages=190–4 |date=January 1978 |pmid=343104 |pmc=411211 |doi=10.1073/pnas.75.1.190|bibcode=1978PNAS...75..190V |doi-access=free }}</ref> and other [[ncRNA]]<ref>{{cite journal |last1=Khan |first1=MR |last2=Wellinger |first2=RJ |last3=Laurent |first3=B |title=Exploring the Alternative Splicing of Long Noncoding RNAs. |journal=Trends in Genetics |date=August 2021 |volume=37 |issue=8 |pages=695–698 |doi=10.1016/j.tig.2021.03.010 |pmid=33892960|s2cid=233382870 }}</ref> and it also was used later for RNA molecules originating from different parts of the genome that are then [[ligation (molecular biology)|ligated]] by trans-splicing.<ref>{{cite journal |vauthors=Liu AY, Van der Ploeg LH, Rijsewijk FA, Borst P |title=The transposition unit of variant surface glycoprotein gene 118 of Trypanosoma brucei. Presence of repeated elements at its border and absence of promoter-associated sequences |journal=Journal of Molecular Biology |volume=167 |issue=1 |pages=57–75 |date=June 1983 |pmid=6306255 |doi=10.1016/S0022-2836(83)80034-5}}</ref>